Conventionally, there is a supporting structure for a vehicle power source used in a vehicle body. Such supporting structure types include a gravity center mount type of supporting structure and an inertia bearing main shaft type of supporting structure.
The gravity center mount type is a type in which a center of elasticity is created through mounts, and is substantially accorded with a gravity center of the supporting structure. In this configuration, an engine and transmission are visually placed and held on the mounts, which are provided on frame members such as a sub-frame.
When the engine is lengthwise disposed, the center of elasticity created by the mounts is set higher than the gravity center of the engine in many cases by tilting mounts disposed at right and left near the gravity center.
An inertia bearing main shaft type includes a plurality of mount members consisting of a front stopper disposed at a front side of an engine, a rear stopper disposed at a back side of the engine, a side engine mount disposed at a side end of the engine, and a transmission mount disposed at a side end of the transmission (for example, refer to Japan patent publication 63-55453).
Here, the front and rear stoppers are secondary weight sharing mount members which do not mainly share the weight of the engine and transmission being a power source.
On the other hand, the side engine mount and transmission mount are primary weight sharing mount members which mainly share the weight of the engine and transmission.
FIG. 1 is a rear view showing a general configuration of a conventional inertia bearing main shaft type of supporting structure. As shown in FIG. 1, although the inertia bearing main shaft type is generally a type of supporting structure which holds the vicinity of a torque roll shaft, mount members 101 are in many cases disposed on a side frame or at its side in the case of a layout in which an engine 102 is laterally disposed. A position of a gravity center 121 in a power source 104 which is a connected body of the engine 102 and a transmission 103 is mostly located under the side frame. Therefore, positions of a side engine mount 112a and transmission mount 112b at both sides of the power source 104 are located above the gravity center of the power source 104 in many cases. Accordingly, a center of elasticity created by the mounts is higher than the gravity center 121 in many cases.
In the gravity center mount type of supporting structure, however, the supporting structure is a type in which the engine and transmission are placed and held on mounts provided on frame members such as the sub-frame, so that the center of elasticity formed by the mounts easily becomes lower than the gravity center consisting of the engine and transmission. Therefore, the power source easily rolls and/or pitches according to movements of a vehicle.
Moreover, there is a problem that a passenger easily experiences a roll/pitch feeling of the power source and cannot get a sense of unity between the power source and vehicle body and so a sufficient drive-safety/ride-quality feeling cannot be obtained.
On the other hand, in a conventional inertia bearing main shaft type of supporting structure shown in FIG. 1, the mount members 101 are disposed on the side frame or at its side. In this configuration, it is difficult to adopt a double vibration isolation structure such that mount members 101 are placed and held on the side frame and elastically supported by a vehicle body frame, compared to the gravity center mount type of supporting structure. Moreover, there is a problem that routes from the side engine mount 112a and transmission mount 112b at both sides to a cabin are short, so a sound and vibration which cannot be completely shut off by the mount members 101 are easily transmitted to a passenger.